Work-related musculoskeletal disorders (WMSDs) of the upper extremity are now a leading cause of lost workday injuries and a significant economic burden to industry. The human cost of a chronic upper extremity injury is hard to measure. Chronic cumulative trauma disorders are incurable. Medical intervention may help repair damage, but individuals stricken with a cumulative trauma disorder of the upper extremity may never completely regain sensitivity, strength, motion and endurance. The economic cost to industry in terms of direct worker?s compensation costs and indirect costs can be over whelming. A single large medical claim can destroy the premium structure of a small company. The annual worker?s compensation claims from high-risk industries can significantly damage company profit margins. Companies can, however, at a fraction of the treatment costs, identify risk factors of upper extremity injuries and through preventative measures protect their profits and their employees.According to the Occupational Health and Safety Administration (OSHA), These WMSDs of the upper extremity account for 34 percent of all lost workday injuries and illnesses. The Bureau of Labor Statistics cites that in 1996, there were 647,000 lost workday WMSDs reported. Carpal Tunnel Syndrome leads on average to more days away from work than any other work place injury. Such cases involve more than 25 days away from work as compared to 17 for fractures and 20 for amputations. (1)In addition, Work-related Musculoskeletal Disorders of the upper extremity account for more than $15 billion to $20 billion in Worker?s Compensation costs annually. These work related upper extremity account for $1 of every $3 spent for Worker?s Compensation.(1) Direct costs of a work related upper extremity injury includes medical treatment and indemnity. Additional indirect costs of a worker?s compensation claim include product line inefficiency, the training and hiring costs of replacement employees and administrative costs. The total direct and indirect costs of upper extremity work-related injuries add up to over $60 billion a year. (1) An individual upper extremity injury claim can destroy the premium structure of a small company, not to mention the damage on profits that these claims make. According to the Wall Street Journal, April 27, 1993, the cost of each individual upper extremity injury exceeds $20,000 on the average. Just one carpal tunnel syndrome case requiring surgery averages $35,000 nationally. The U.S. Department of Labor 1992 report cites the average compensation of a repetitive strain injury as $29,000. The burden of upper extremity injuries in terms of economic costs and human suffering are apparent. Often the suffering by repetitive strain injuries is needless. Companies can prevent most work-related injuries by identifying associated risk factors and implementing prevention strategies. These risk-reduction programs can protect company profits and their employees.A risk factor is any attribute, experience or exposure that increases the probability of occurrence of a disease or disorder, though it is not necessarily a causal factor. Several recent biomechanical and epidemiological studies have identified a range of occupational and non-occupational risk factors associated with the prevalence of upper extremity injuries.

Occupational Factors:Recent studies have identified the following occupational factors as potentially contributing to the development of upper extremity cumulative trauma injuries:1. High Task Repetition and Inappropriate Work / Rest Cycles: A job is classified as highly repetitive if the cycle time is less than 30 seconds, or if a task or motion is performed more than 50% of the time it takes to complete the work cycle. Work and rest cycles are the intervals of time measured during one complete task revolution or cycle. The more repetitive the task or cycle, the less recovery time there is for the muscles and tendons. Inappropriate rest/work cycles are work cycles that do not allow time for sufficient recovery and micro trauma can accumulate, leading to cumulative trauma disorders.2. Forces and Forceful Exertions: Both static and dynamic loading increases muscle contraction strength and duration, thus reducing circulation to the muscle fibers and increasing recovery time requirements. Static loading is a greater risk factor than dynamic loading, since static loading results in increased muscle fiber recruitment and fatigue and decreased blood perfusion. Forceful exertions produce increased muscle effort in response to high task load, leading to more rapid muscle fatigue and overuse which can lead to upper extremity injuries. (2)3. Positions of the Wrist and Arm and Awkward Postures: Repetitive wrist flexion and extension increase intra-carpal tunnel pressures in the wrist. In addition, awkward postures overload muscles and tendons and load joints in an asymmetrical manner, imposing a static load to the musculature thus reducing nerve and muscle blood flow. (3) Activities that use repetitive finger motions with the wrist in an extended position in constrained postures, such as playing a musical instrument, typing or the use of pinch grips also increases intra-carpal tunnel pressures and thus reduces nerve and muscle blood flow which may lead to upper extremity injuries. ( 4)4. Mechanical Stress Concentrations / Contact Trauma: Weight bearing with the wrist in an extended position such as gymnastic sports or bicycle riding. Direct pressure contacting the base of the palm or the palmar surface of the fingers such as in frequent or continuous use of tools with hard or sharp edges, or short handles can cause direct compression against peripheral nerve fibers, leading to upper extremity symptoms. (5)5. Vibration Forces on the Wrist and Hand: Vibrating hand-held tools can cause toxic vibration reflex (6) and constrict blood vessels, which may damage nerve fibers in the upper extremity. (7) 6. Exposure to Cold: Working in cold environments and/or handling cold tools affect the circulation to the upper extremity. (7)7. Gloves: Use of gloves reduces tactility, increasing the amount of force required to hold or manipulate a given object. This risk increases with poor fitting of the gloves and with glove thickness. (7)8. Lead: Constant contact or exposure to lead has been shown to impair maximal motor and sensory nerve conduction velocities of the medial nerve which may cause Carpal Tunnel Syndrome of the wrist. (8)9. Work Stress and Job Satisfaction: The perception of the workload, work pressures and job satisfaction may alter the individual?s response to early signs of fatigue and discomfort. (9)

The risk of developing upper extremity cumulative trauma injuries increases with the number of risk factors present. Jobs that combine high force and high repetition pose the greatest risk.Individual Factors:Upper extremity cumulative trauma injuries can be occupationally and non-occupationally induced or it can be a combination of activities. In addition, individual anatomy and physiology differences may also increase risk for upper extremity injuries. It is difficult to isolate occupational factors from leisure activities and individual susceptibility. However certain conditions and disorders coexist with some upper extremity syndromes. Some injuries of the upper extremity can occasionally be associated with past or present history of systemic illnesses and acute trauma to the region. 1. Inflammatory / Autoimmune Disorders: Rheumatoid arthritis, polymyalgia, tenosynovitis and Lupus erythematosis are associated with increased incidence of cumulative trauma disorders of the upper extremity. (10)2. Hormonal / Metabolic Disorders: Use of oral contraceptives, pregnancy, renal failure, obesity, menopause, hypo and hyperthyroidism and post hysterectomy patients. It is thought that the increased incidence of cumulative trauma injuries of the upper extremity are due to altered hormonal balances causing connective tissue changes similar to an inflammatory response. (11)3. Systemic Diseases: Other systemic disease associated with an increased risk for upper extremity injuries include: hypertension, kidney disorders and cystic fibrosis. (12) In addition, Diabetes mellitus and alcoholism are associated with increased risk for upper extremity injuries. (10)4. Vitamin Deficiency: Vitamin B complexes have been found beneficial to patients with carpal tunnel syndrome. (13)5. Non-Medical Factors: Females represent about two thirds of reported Workers compensation cases. (1)6. Body Mass Index: Increased weight and body mass index (BMI) have been suggested as personal risk factors for carpal tunnel syndrome and other cumulative trauma injuries to the upper extremity. 7. Hereditary Traits: There is some evidence that genetic traits may be an important part of acquiring cumulative trauma disorders of the upper extremity. (14)8. Traumatic Causes: Occasionally upper extremity injuries can be caused by direct trauma to the wrist or hand. Direct trauma mechanisms include: Hematoma due to hemorrhage, carpal dislocation, fracture or the immobilization following a fracture repair. (10)9. Non-Traumatic Causes: Additional non-traumatic causes include: tumors and variations in anatomy that may increase individual susceptibility for an upper extremity injury. (10)

The cause of an upper extremity injury may be of unknown etiology, secondary to trauma or a systemic disease, secondary to other individual factors or a sequelae of work factors such as repetitive work activities with inadequate work-rest ratios and task variations and /or excessive force. Upper extremity injuries can also be aggravated by any combination of the above-identified risk factors. To protect employees from Work-related Musculoskeletal Disorders in the workplace, as well as company profit margins, companies should implement a risk reduction program targeted at identifying risk and implementing risk reduction strategies. Companies can reduce upper extremity strain and protect against high cost injuries.